feat: 10-band EQ, connection indicator, new icon (v1.5.0)

### 10-Band Graphic Equalizer
- Full EQ in Rust audio engine via EqSource<S> biquad peak filters
- 10 built-in presets + custom preset save/delete
- EqSource::try_seek() implemented — also fixes waveform seek which broke
  silently when EQ was introduced (rodio returned SeekError::NotSupported)
- EQ state persisted in localStorage, synced to Rust on startup

### Connection Indicator
- LED in header (green/red/pulsing) with server name and LAN/WAN label
- Offline overlay with retry button when server is unreachable
- useConnectionStatus hook

### New App Icon
- New logo (logo-psysonic.png) applied across Login, Sidebar, Settings,
  README and all Tauri platform icons (Windows, macOS, Linux, Android, iOS)

### Now Playing Page
- New /now-playing route added

### Fixes
- WaveformSeek: mousemove/mouseup on window to fix drag outside canvas

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/pages/Artists.tsx

@@ -161,7 +161,7 @@ export default function Artists() {
                 <div className="artist-card-avatar artist-card-avatar-initial" style={{ borderColor: color }}>
                   <span style={{ color }}>{nameInitial(artist.name)}</span>
                 </div>
-                <div>
+                <div style={{ textAlign: 'center' }}>
                   <div className="artist-card-name">{artist.name}</div>
                   {artist.albumCount != null && (
                     <div className="artist-card-meta">{t('artists.albumCount', { count: artist.albumCount })}</div>